If you type site:svg.nicubunu.rointo Google Search, you can see that only the home page was ever indexed, and it does not even show a description on the SERP. And if you view the cached page, you can see that Google doesn't understand any of the layout of the page.

If Google's advanced crawler is having trouble with SVG websites, I can guarantee that more basic crawlers like Bing and Yahoo will have even greater trouble with it.

So, a website built entirely in SVG will perform poorly in regards to SEO. And aside from SEO, a website built entirely in SVG is much more difficult (or impossible?) to make look good on both desktop and phone browsers.

It seems that this question – and, therefore, answer – being featured on the Hot page of SE has overwhelmed the site you linked.
– pytagoJan 11 at 13:11

4

Wow, that website you linked is super annoying. You can only select text for an extremely short period of time, probably only one frame. And the order the text is selected in is pretty chaotic, the title comes after one of the middle paragraphs for example. And my Chrome extension that gives every website a black theme just completely gives up on it, in all four modes. Same with my adblocker, it doesn't even show the menu for blocking custom elements. And there's a spelling error. But hey, at least there's no custom font smoothing, that's one advantage, I guess.
– Fabian RölingJan 12 at 15:45

I've search around a bit, but there doesn't seem to be any change that I'm aware of, so it's probably still true. In any case, xlink:href is depreciated in favor of just an href attribute which Google does follow so you should be all right.

Conclusion: There should be minimal effect on how your pages are indexed as long as you make sure your links are actually crawlable. All three search engines were able to find the text on the pages they indexed. I haven't tested other aspects of SEO but neither indexing or searchability seems to be an issue.